The fact that the attenuation of low loss optical fibers tends to be especially low in the wavelength region between 1.3 and 1.6 microns has created a need for photodetectors efficient at such wavelengths. Of particular interest are avalanche photodetectors because of the intrinsic gain they provide. Hitherto it has proven difficult to realize sensitive avalanche photodetectors useful at wavelengths longer than 1.25 microns. In particular, in prior art devices designed for use at such long wavelengths, at voltages where photocurrent gain is realized, the tunneling currents and resultant shot noise tend to be large, limiting the sensitivity improvement of receivers using such detectors.